Method of adjusting two electrode surfaces in an electric discharge tube at a given distance from each other

ABSTRACT

A method of adjusting two metallic electrodes surfaces in an electric discharge tube at a given distance from each other in which an intermediate layer of non-metallic material, e.g. carbon or a metal oxide, is provided between the surfaces of the electrodes which are placed in abutting relationship. The electrodes are then heated to a temperature of about 780*C to connect them with supporting members and cooled. Due to different coefficients of expansion of the electrodes and supporting members, the electrodes separate and the intermediate layer is then removed.

United States Patent [19] van Esdonk et al.

METHOD OF ADJUSTING TWO ELECTRODE SURFACES IN AN ELECTRIC DISCHARGE TUBE AT A GIVEN DISTANCE FROM EACH OTHER Inventors: Johannes van Esdonk; Johannes Hendrikus Theodorus van Roosmalen, both of Emmasingel, Eindhoven, Netherlands Assignee: U.S. Philips Corporation, New

York, N.Y.

Filed: May 24, 1971 Appl. No.: 146,108

Foreign Application Priority Data June 25, 1970 Netherlands ..7009324 US. Cl. ..29/25.l6, 29/2513, 29/493 rm. c1 ..l-l01j 9/18 Field of Search ..29/497.5, 25.1, 25.11,

[451 Apr. 17, 1973 [56] References Cited UNITED STATES P'ATENTS 2,992,480 7/ l 961 Spencer ..29/497.5 3,643,299 2/1972 Brown ..29/25 .16 3,298,083 l/l967 Kelly ..29/25.l6 3,279,029 10/1966 Stern ..29/25. 1 6

Primary Examiner-J. Spencer O'verholser Assistant Examiner-Richard Bernard Lazarus AttorneyFrank R. Trifari [57] ABSTRACT A method of adjusting two metallic electrodes surfaces in an electric discharge tube at a given distance from each other in which an intermediate layer of non-metallic material, e.g. carbon or a metal oxide, is provided between the surfaces of the electrodes which are placed in abutting relationship. The electrodes are then heated to a temperature of about 780C to connect them with supporting members and cooled. Due to different coefficients of expansion of the electrodes and supporting members, the electrodes separate and the intermediate layer is then removed.

4 Claims, 2 Drawing Figures METHOD OF ADJUSTING TWO ELECTRODE SURFACES IN AN ELECTRIC DISCHARGE TUBE AT A GIVEN DISTANCE FROM EACH OTHER The invention relates to a method of adjusting two metallic electrode surfaces in an electric discharge tube at a given distance from each other, in which said surfaces are arranged against each other and are heated together with their supporting members to above the operating temperature and connected to said members, after which the desirable distance is obtained by the difference in expansion between the electrode and the supporting members, after cooling to the operating temperature.

The invention furthermore relates to an electric discharge tube, in particular a camera tube, comprising at least two electrodes the mutual distance between the surface of which has been adjusted by means of said method.

From Dutch Pat. specification No. 69406, British Pat. specification No. 567,111, and German Pat. specification No. 892,642 it is known to adjust electrode surfaces at a small distance from each other by arranging said electrodes with their operative surfaces against each other, heating them together with their supporting members to above the operating temperature, and rigidly connecting the electrodes at the said high temperature to the supporting members, for exam ple, by means of solder, after which the desired electrode distance is obtained, after cooling to the operating temperature, by the difference in expansion between the electrodes and the supporting members.

Difficulties have been found to occur, however, since the electrode surfaces engaging each other start sticking together at the high temperature. This is probably a result of diffusion phenomena. If the electrode surfaces upon cooling are drawn apart as a result of the difference in expansion between the electrodes and the supporting members, deformation of or damage to the electrodes may occur.

This sticking together of the electrode surfaces arranged against each other can be fully avoided by using the above method if, according to the invention, at least one of the surfaces which are to be arranged against each other is at least partly covered with a layer of separate particles of a non-metallic material, which after cooling of the electrodes, is removed from between the electrode surfaces.

The layer preferably consists of carbon which is provided on one of the electrode surfaces in the form of soot or graphite as a very thin layer in a thickness of less than l,/L. However, the layer may also consists of particles or grains consisting ofa metal oxide which can be provided on the surface in a suitable manner, for example by cataphoresis, as a fume or by sputtering in an oxidizing atmosphere. However, this material must afterwards be removed from between the electrode surfaces, and this may be carried out by means of ultrasonic vibrations in or by rinsing with a suitable liquid, for example, water, or a suitable hydrocarbon compound, which does not attack the material of the electrodes or of the supporting members and does not leave any residues after drying.

The invention will now be described with reference to the accompanying drawing, in which FIG. 1 is a longitudinal cross-sectional view of two electrodes prior to heating, while FIG. 2 is a longitudinal cross-sectional view of the electrodes as they can be incorporated in a discharge tube.

Reference numeral 1 in FIG. I denotes a control electrode, 2 is an anode of an electron gun of a camera tube. On the outersurface of the electrodes, moulded or compressed annular parts 3 having an upright edge are secured. The rings 3 may also be replaced, however, by angle pieces. The upright edge of each ring 3 comprises three apertures through which supporting members of insulating material in the form of ceramic rods 4 are slid.

In order to prevent the rods 4 from dropping out of the apertures, incisionsare provided in the rings 3 so that lugs 10 are obtained which can be bent upwards. Each rod 4 is metallized at its ends. After providing the rods 4 in the apertures of the rings 3, soldering material 9 is provided on the metallisation 5 of the rods 4, for example, as rings or as a paste. Plates 6 and 7 are secured to the electrodes 1 arid 2, for example by welding or soldering. The plates 6 and 7 constitute the active electrode surface and must be arranged at a mutual distance of approximately 10 p. at the operating temperature and be connected to the supporting members 4.

For that purpose, the outer surface of the plate 6 is covered with a thin granular layer 8 of carbon. This carbon layer 8 has a thickness of less than 1 p. and must not constitute a solid closed layer, but consist of separate particles which can be removed afterwards.

The electrodes 1 and 2 are placed in a jig with their surfaces 6 and 7 against each other and are heated at 780C. At this temperature the soldering material 9 melts so that the electrodes are connected to the sup-:

porting members 4, since upon cooling, the soldering material 9 solidifies already at a slight temperature drop.

Since the metal electrode 2 has a much larger thermal expansion than the ceramic rods 4, the electrodes 6 and 7 will be slightly spaced apart. at room temperature. This distance is larger than the desirable distance at the operating temperature.

In this case the surfaces 6 and 7 of the electrodes are at a distance, for example, of 2(1) u. The intermediate layer 8 is then removed by means of ultrasonic vibrations in or by rinsing with a suitable liquid, for example, water or a hydrocarbon compound, for example hexane, which dries up without leaving residues.

Since the expansion of the ceramic rod 4 is very constant and the electrodes with the rod can be uniformly heated in an oven since the rods do not soften, the surfaces of the plates 6 and 7 remain truly parallel to each other. Since as a result of the presence of the layer 8 said surfaces do not stick together during heating, they a will not experience any deformation upon separating them.

Although one embodiment has been described, the

invention may also be applied to other embodiments of metal electrodes and supporting members. The invention is of particular importance if the metal parts facing each other have a very small wall thickness.

What is claimed is:

1. A method of adjusting two metallic electrode surtrodes and supporting members, and thereafter removing the layer of non-metallic material on the surface of the electrodes.

2. A method as claimed in claim 1, wherein the intermediate layer consists of carbon.

3. A method as claimed in claim 1, wherein the intermediate layer is a metal oxide.

4. A method as claimed in claim 1, wherein the intermediate layer is removed ultrasonically in a bath containing a suitable liquid. 

1. A method of adjusting two metallic electrode surfaces in an electric discharge tube at a given distance from each other comprising the steps of at least partly covering one surface of at least one of the electrodes with a layer of separate particles of a non-metallic material, positioning said electrodes wiTh the surfaces in substantially abutting relationship and the layer of non-metallic material therebetween, heating said electrodes to a temperature of about 780*C to connect them to support members having a different coefficient of expansion than that of said electrodes, cooling said electrodes and supporting members to thereby space the electrodes a given distance from each other as a result of the difference in expansion between the electrodes and supporting members, and thereafter removing the layer of nonmetallic material on the surface of the electrodes.
 2. A method as claimed in claim 1, wherein the intermediate layer consists of carbon.
 3. A method as claimed in claim 1, wherein the intermediate layer is a metal oxide.
 4. A method as claimed in claim 1 wherein the intermediate layer is removed ultrasonically in a bath containing a suitable liquid. 